JPS5820709A - Silicon carbide furnace - Google Patents

Abstract

A furnace for manufacturing silicon carbide comprises a broken ring (8) of raw materials in which is embedded a graphite electrical heating element (12). The ring (8) is free-standing and defines a central working space (32) in which is located a support (36). The furnace is enclosed by an annular wall (44) spaced from the ring (8) to define an annular working space. A track (38) is mounted on top of the wall (44) and a rotatable materials handling device (6) is mounted on the central support (36) and the track (38). Materials are discharged from an outlet (48) to form the ring (8) as the device (6) rotates. A geodesic dome roof prevents escape of pollutants to atmosphere.

Description

[Detailed description of the invention] The present invention relates to a silicon carbide manufacturing apparatus.

Silicon carbide is produced from a mixture of carbon and silica or silicon under various time and temperature conditions. The lowest temperature is 525℃, from silicon and carbon, silicon with a lot of carbon, and aluminum.

Manufactured under specific conditions from an alloy of zinc. Silicon carbide crystals have been produced by gaseous cracking methods in at least five types of deposition equipment. The main manufacturing method is maximum length 1
5 Q ft (approx. 18m) Width 1[] ft (approx. 3m)
', the mixture of sand and coke is made up to 2000001d
(approximately 9 otyL) is produced in a holding sulkhatchi type furnace. The furnace walls are usually cast iron framed and lined with low-quality refractory bricks and can be removed and disassembled. Member power, 6 adult rats.

This reactor, commonly known as the Aaga-7 Reactor, has essentially remained unchanged for the past 70 years.

The mixed materials are charged to the furnace by a hopper and overhead lanes or conveyors. When the furnace is about half full, charging is temporarily stopped and a core of bulk graphide is placed between the electrodes at both ends of the furnace. The core has a uniform cross-sectional area9, e.g. a thickness of about 1
0in, (approximately 25'Omm) width approximately 16in, (approximately 400
mm) and vary depending on the dimensions of the furnace. Place the remainder of the mixture on the core to complete the charge. A typical furnace requires about 4 people to charge the mixture at a rate of 40-45%. That is.

The productivity is 10-11 wax/man-hour.

Maximum power supply is 5000kW, voltage Fi500
~200V, and the resistance of the charge changes over a heating period of about 1.5 days. The heated charge is allowed to cool for several days until it reaches a temperature at which it can be handled. When the sidewalls are removed, the excess charge collapses and exposes the ingot. The collapsed charge has the same composition as the original mixture.

Can be occupied exclusively. The ingot has an oval cross section.

Cover with a crust about 1-2 inches (about 25-50 inches) thick. The temperature gradient at this location favors the concentration of oxide impurities, resulting in the formation of a relatively thin crust. Due to this concentration, unwanted impurities can be effectively discarded.

The ingot itself contains marketable silicon carbide crystals and is broken into large pieces and removed from the furnace. The graphide core will be collected and sent to Furukawa as core material. The crystal ingot is crushed and passed through a sieve into the required size. Depending on the use, the nine particles are washed with acid or alkali, washed with water, and dried. The above procedure is known as the Acheson method.

The above-mentioned furnaces typically require 4 to 6 furnaces for each transformer to operate the transformers at maximum efficiency. That is, the first furnace is for heating, the second is for taking out, and the third is for charging.

The rest is cooling down. For this reason, the equipment costs for buildings and furnaces are extremely high. Removing this furnace is extremely difficult and time consuming. There is a high-temperature furnace nearby, and when removing silicon carbide from the furnace, the distance between the adjacent furnaces is small and it is difficult to use a mechanical extraction device, so the amount of manual work required is extremely large.

For this reason, the cooling time of the furnace before taking it out is extremely long because it cools down to a temperature that allows 9 manual operations. Furthermore, problems arise when charging the furnace. Because of the adjacent furnaces, either a long conveyor belt is extended from the mixing device to the furnace, or an overhead crane transports the packets one after another to the furnace. This entire process requires 6 to 7 days from startup to completion.

A typical installation would be six furnaces per transformer, requiring 40 to 50 people in consecutive shifts for six transformers.

The furnace of the present invention can significantly reduce operating costs, moderate power usage, and charge rate of 100-110 yuan per person hour. 1
The 0x productivity is obtained from the new design of the furnace, which uses automated material handling equipment to charge the mixture into the furnace. Furthermore, the apparatus of the present invention allows the use of a large machine such as a packet loader when unloading from the furnace.

It is an object of the present invention to provide a new furnace design using the principles of the Acheson process.

Another object of the present invention is to provide a new silicon carbide manufacturing equipment.

Another object of the invention is to reduce operating costs of silicon carbide furnaces by increasing productivity and optimizing power usage.

Another object of the invention is to provide effective contaminant control for silicon carbide facilities.

Another object of the invention is to reduce electrical losses.Another object of the invention is to reduce the risks associated with furnace operation.

Another purpose is to improve material handling.

In the electric resistance furnace according to the invention, silicon carbide is produced by direct electrical heating from a charge of stone substance and carbonaceous material. Current is supplied via the busbar and electrodes to a carbon resistive core inserted horizontally into the charge. The core and charge are in the form of an incomplete ring.

The heating chamber housing the electric resistance furnace shall be dimensioned to allow operation. A charging and unloading device is installed in the furnace. The upper part of the chamber is closed and a duct is connected to the dust collection chamber.

Practical examples and drawings illustrating the present invention will be described.

1 and 2 show a silicon carbide manufacturing apparatus according to the present invention, in which a heating furnace apparatus is installed in a heating chamber of a building 2. As shown in the diagram, the building is dome-shaped.

A suitable example is a geodesic dome (geodesic dome).
ome). A conveyor (not shown) transports the raw materials, that is, the stone substance and carbonaceous material mixed in a required ratio, from the main building to the heating chamber. This conveyor supplies material to the material handling device 6 from a transverse conveyor (not shown). Handling device 6
9 is above the incomplete ring furnace of the present invention. Handling device 6
In this case, 100 raw materials are charged into the furnace 8. Furthermore, the grahyde core 12 is placed at a required position relative to the material. The furnace is a dormant square furnace and does not use side walls or gates to accommodate the loading material. Side walls can also be provided as required.

Furthermore, the shape of the furnace 8 is an incomplete ring shape.

A central working space 32 is formed. Material handling device 6 includes a rotating loading member 64 . One end of the member 64 is rotatably supported on a post 66 in the center of the workspace 62. A car 42 or the like is attached to the other end of the member 34. Side wall 4 of building 2
A car 42 is supported on a circumferential track 28 attached to the inner surface of the car 4. The loading member 64 has a discharge chute 4 that corresponds to the core 12.
It has 8. As the loading member 34 rotates about the central post filter 6, the material falls through the chute 48 in a soring-like pattern. However, the sector of the ring is open, forming an incomplete ring and easily entering the two working spaces 32.

When charging the furnace, the bottom section is formed first and then stopped. The reactor core 12 is then placed on top of the mixture. Next, continue charging to form a triangular shape.

When charging is completed, a power source, such as a transformer 14, is connected to electrodes 16 at both ends of the furnace via a bus bar 16. Since the furnace is almost a complete ring and the transformer is located near the end wall 20 of the furnace, the length of the bus bar is significantly short. The transformer powers the furnace shown and also powers the furnaces 22 in the other heating chambers 24 to start up when the first furnace has cooled. The power passing through the busbars, electrodes, and core may be alternating current or direct current. The required electrical power generates temperatures that cause the quartzaceous, carbonaceous materials to react and form silicon carbide.

Once the heating cycle is complete, transformer 14 is shut off.

Start the cooling removal process. The procedure for cooling and removing the furnace is as follows. First, the furnace deposit is allowed to cool for several days. Here,
A device such as a power shovel, such as a front end loader 26, is placed into the furnace. This device sequentially breaks down the deposits and removes them from the furnace. Because the furnace is in the shape of an incomplete ring, the power shovel enters the work space 62 through the opening between the end walls 20. A shovel 26 is used to mechanically break up the deposits. In conventional silicon carbide furnace designs, the unloading and most charging procedures use expensive and time consuming procedures. The demolition operation continuously exposes the hot material under the deposit to air. Once the excess deposits in the furnace have been removed and the silicon carbide ingot is exposed, it is allowed to cool for several days. Water spray can be used to aid cooling. After the cooling process, the same equipment is used to remove the ingots and send them to the central cleaning and sorting equipment. Once the ingot is removed from the furnace, the charging cycle is repeated.

Contaminants formed during the charging, heating and unloading processes are removed from duct 2.
8 to be collected and processed in an auxiliary device 30 forming a contaminant treatment station. Emissions from the device 3° meet national environmental standards. Historically, pollutants emitted from silicon carbide firing equipment have been a major problem in the industry. No other equipment can effectively handle contaminant problems throughout the firing process. All walls of the dome 2 are impermeable and all contaminants formed during the process are contained within the building and are not released into the atmosphere.

The walls of the building 2 are circular, and the furnace 8 is also circular, so
A second working space 46 is formed in the middle. As shown in Figure 1,! The dowel 26 passes through the second workspace and directs the excess deposits to a passing device 50 and to a material feeder for use by the horses.

The above-described equipment reduces the operating costs of silicon carbide production. Labor costs are low. Short bus bars reduce material costs and electrical loss. Contaminant control is easy. It is easy to load and unload the furnace. Since the operator does not need to enter the heating chamber while the furnace is operating, there is significantly less danger during the operation.

The cross-sectional view shown in FIG. 3 shows a relatively new silicon carbide furnace that overcomes some of the problems associated with conventional Acheson furnaces. This known furnace 52 is disclosed in US Pat. No. 4,158,744.
The U-shaped resistive core 54 is completely surrounded by a reactive material 56. Because the furnace of the present invention is generally ring-shaped, it can be loaded by automatic material handling equipment, such as the loading device 34 shown in the figures. The furnace configuration shown in FIGS. 1-2 allows relatively simple single point rotation equipment to be used to charge the furnace. This simple single point rotation device cannot be used in known U-type furnaces. The U-shape is a combination of a semicircle and two parallel legs. Furthermore, known furnaces require electrically insulating material to be placed between the electrodes to prevent current leakage between the parallel straight legs. This insulating material becomes a contaminant to the material of the reaction deposit. Insulators are required because the reactive material between the legs forms a path for electrical flow. The configuration of the present invention does not require insulating material between the electrodes 16 because the graphide core and the overlying reactive material are separated from the electrodes at a large angle. The air within the workspace 32 forms a natural insulator to prevent accidental current leakage.

As can be seen in Figures 1 and 2, the furnace of the present invention allows both electrodes to be placed relatively close together, reducing the length of the bus bar and preventing electrical losses. The shape of the furnace allows the use of relatively simple material handling equipment for loading and unloading.

Production output per unit of personnel is 1000% compared to known equipment
will increase.

As a simple example, approximately 50 inches in diameter (approximately 75 crrL)
) A small furnace was built on a flat bed of refractory bricks. Approximately 6 inches (approximately 15 cr/l) wide on a 30 inch circle,
A layer of sand, coke, and raw material mixture approximately 2 (approximately 50ii) deep was formed. K I x 11 inches on the axis of the bed;
Place a graphite core measuring approximately 25 x 31 m) and connect 2 inch (approximately 50 mm) gravite rods to both ends.

A 50 cubic meter transformer was connected to the rod. 6 in. on core.

(approximately 150111) thick mixture by adding 30 in.
.

(approximately 750 mm) diameter ring with a triangular cross section. After heating and cooling, a silicon carbide ingot in the shape of an incomplete ring with a uniform cross section was obtained.

The embodiments and drawings described above are illustrative and do not limit the invention.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a silicon carbide production facility according to the present invention, FIG. 2 is a sectional view of a part of the facility of FIG. 1, and FIG. 6 is a sectional view of a known furnace. 2: Building 6: Material handling equipment 8.22, 52
: Furnace 10: Raw material 12.54: Granite reactor core (core) 14: Transformer 20: End wall 24: Heating chamber 28: Duct 32, Filter 4: Working space Filter 4: Rotating loading member 36 =
Strut Patent Applicant: Dresser Industries, Inc. 7B 11 FIG, /

Claims (1)

[Claims] 1. A silicon carbide production device with a power source. a furnace chamber; an electric resistance furnace installed in the furnace chamber and operated by electric heat to produce silicon carbide from a charge of stone substance and carbonaceous material; inserted horizontally into the charge and supplied with electric current through electrodes; A carbon resistance reactor core is provided, in which the core and the charge are formed into an incomplete ring shape to form a central circular working space, and a device is provided for charging the reactor core into the reactor in the incomplete ring shape. Silicon carbide manufacturing characterized in that the charging device includes a material handling device that is rotatably supported around the center of the work space and charges materials surrounding the reactor core, and is equipped with an unloading device from the furnace. Apparatus 02, wherein the wall of the furnace chamber is ring-shaped and spaced apart from the furnace to form a second annular working space coaxial with the central working space and spaced radially outwardly between the furnace and the furnace. The device according to paragraph 1. 6. An electrothermally operated electric resistance furnace for producing silicon carbide from a freely placed charge of stone-like and carbonaceous materials, the electrode being connected to a resistive core of carbon inserted horizontally into the charge. The core and the charge are formed into an incomplete ring to form a central working space. A silicon carbide production apparatus characterized in that the charge is placed freely and its shape is not restricted. 4. The charging device includes a device for charging the furnace in an incomplete ring shape, and the charging device includes a material handling device that supports the material rotatably around the center of the work space and charges the material surrounding the core. 4. The apparatus of claim 3 comprising: 5. Power supply for silicon carbide production equipment. A freely disposed charge of stone parenchyma and carbonaceous material deposited in an incomplete ring in the chamber to form a central circular working space, a power source containing two spaced electrodes, and a material deposit within the material deposit. A resistor core is inserted horizontally and has an incomplete ring shape with both ends spaced apart, and nine electrodes are connected to one of the ends of the core respectively, and a current supplied from a power source is passed through the electrodes to the resistor core to remove the material. a dome with a non-combustible base fully formed and a circumferential track connected to the inner surface of the side wall; and a material handling device for charging the charge in the form of an incomplete ring as a material deposit; The handling device includes a support device in the center of the working space, a loading device rotatably supported at one end on the support device and discharging the rotational amount of material to form an incomplete ring-shaped pile; A silicon carbide production device characterized in that the other end is supported by a track to enable relative movement with the dome. 6. Said dome is such as to prevent any contaminants that form during the charging, heating and unloading of the material from escaping into the atmosphere, and a device is installed within the dome to collect the contaminants and transport them to a processing station remote from the dome. An apparatus according to claim 5 provided. Z. The device according to claim 5 or 6, wherein the dome is a geodesic dome. 8. Claims in which the side walls of said dome form a second annular working space coaxially spaced radially outwardly from said free-standing pile to a central working space. The device according to paragraph 5.